1 files changed, 498 insertions, 0 deletions
diff --git a/kernel/features/mm.c b/kernel/features/mm.c
new file mode 100644
index 0000000..9eca438
--- /dev/null
+++ b/kernel/features/mm.c
@@ -0,0 +1,498 @@
+// Hugely inspired by the implementation in skiftOS: MIT License, Copyright (c) 2020 N. Van Bossuyt
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#include <assert.h>
+#include <cpu.h>
+#include <def.h>
+#include <mem.h>
+#include <mm.h>
+#include <print.h>
+
+static struct page_dir kernel_dir ALIGNED(PAGE_SIZE) = { 0 };
+static struct page_table kernel_tables[256] ALIGNED(PAGE_SIZE) = { 0 };
+
+/**
+ * Lowlevel paging
+ */
+
+/*static void paging_disable(void)
+{
+	cr0_set(cr0_get() | 0x7fffffff);
+}*/
+
+static void paging_enable(void)
+{
+	cr0_set(cr0_get() | 0x80000000);
+}
+
+static void paging_switch_dir(u32 dir)
+{
+	cr3_set(dir);
+}
+
+extern void paging_invalidate_tlb(void);
+
+void page_fault_handler(struct regs *r)
+{
+	// Check error code
+	const char *type = (r->err_code & 1) ? "present" : "non-present";
+	const char *operation = (r->err_code & 2) ? "write" : "read";
+	const char *super = (r->err_code & 4) ? "User" : "Super";
+
+	// Check cr2 address
+	u32 vaddr;
+	__asm__ volatile("movl %%cr2, %%eax" : "=a"(vaddr));
+	struct proc *proc = proc_current();
+	struct page_dir *dir = NULL;
+	if (proc && proc->page_dir) {
+		dir = proc->page_dir;
+		printf("Stack is at %x, entry at %x\n", virtual_to_physical(dir, proc->regs.ebp),
+		       virtual_to_physical(dir, proc->entry));
+	} else {
+		dir = &kernel_dir;
+	}
+	u32 paddr = virtual_to_physical(dir, vaddr);
+
+	// Print!
+	printf("%s process tried to %s a %s page at [vaddr=%x; paddr=%x]\n", super, operation, type,
+	       vaddr, paddr);
+
+	isr_panic(r);
+}
+
+/**
+ * Physical
+ */
+
+static u32 memory_used = 0;
+static u32 memory_total = 0;
+static u32 best_bet = 0;
+static u8 memory[PAGE_COUNT * PAGE_COUNT / 8] = { 0 };
+
+static u8 physical_page_is_used(u32 addr)
+{
+	u32 page = addr / PAGE_SIZE;
+	return memory[page / 8] & (1 << (page % 8));
+}
+
+static void physical_page_set_used(u32 address)
+{
+	u32 page = address / PAGE_SIZE;
+
+	if (page == best_bet)
+		best_bet++;
+
+	memory[page / 8] |= 1 << (page % 8);
+}
+
+static void physical_page_set_free(u32 address)
+{
+	u32 page = address / PAGE_SIZE;
+
+	if (page < best_bet)
+		best_bet = page;
+
+	memory[page / 8] &= ~(1 << (page % 8));
+}
+
+static void physical_set_used(struct memory_range range)
+{
+	assert(PAGE_ALIGNED(range.base) && PAGE_ALIGNED(range.size));
+
+	for (u32 i = 0; i < range.size / PAGE_SIZE; i++) {
+		u32 addr = range.base + i * PAGE_SIZE;
+		if (!physical_page_is_used(addr)) {
+			memory_used += PAGE_SIZE;
+			physical_page_set_used(addr);
+		}
+	}
+}
+
+static void physical_set_free(struct memory_range range)
+{
+	assert(PAGE_ALIGNED(range.base) && PAGE_ALIGNED(range.size));
+
+	for (u32 i = 0; i < range.size / PAGE_SIZE; i++) {
+		u32 addr = range.base + i * PAGE_SIZE;
+
+		if (physical_page_is_used(addr)) {
+			memory_used -= PAGE_SIZE;
+			physical_page_set_free(addr);
+		}
+	}
+}
+
+static u8 physical_is_used(struct memory_range range)
+{
+	assert(PAGE_ALIGNED(range.base) && PAGE_ALIGNED(range.size));
+
+	for (u32 i = 0; i < range.size / PAGE_SIZE; i++) {
+		u32 addr = range.base + i * PAGE_SIZE;
+
+		if (physical_page_is_used(addr))
+			return 1;
+	}
+
+	return 0;
+}
+
+struct memory_range physical_alloc(u32 size)
+{
+	assert(PAGE_ALIGNED(size));
+
+	for (u32 i = best_bet; i < ((memory_total - size) / PAGE_SIZE); i++) {
+		struct memory_range range = memory_range(i * PAGE_SIZE, size);
+
+		if (!physical_is_used(range)) {
+			physical_set_used(range);
+			return range;
+		}
+	}
+
+	panic("Out of physical memory!\n");
+	return memory_range(0, 0);
+}
+
+void physical_free(struct memory_range range)
+{
+	assert(PAGE_ALIGNED(range.base) && PAGE_ALIGNED(range.size));
+	physical_set_free(range);
+}
+
+/**
+ * Virtual
+ */
+
+#define PDI(vaddr) (((vaddr) >> 22) & 0x03ff)
+#define PTI(vaddr) (((vaddr) >> 12) & 0x03ff)
+
+u8 virtual_present(struct page_dir *dir, u32 vaddr)
+{
+	u32 pdi = PDI(vaddr);
+	union page_dir_entry *dir_entry = &dir->entries[pdi];
+	if (!dir_entry->bits.present)
+		return 0;
+
+	struct page_table *table = (struct page_table *)(dir_entry->bits.address * PAGE_SIZE);
+
+	u32 pti = PTI(vaddr);
+	union page_table_entry *table_entry = &table->entries[pti];
+
+	return table_entry->bits.present;
+}
+
+u32 virtual_to_physical(struct page_dir *dir, u32 vaddr)
+{
+	u32 pdi = PDI(vaddr);
+	union page_dir_entry *dir_entry = &dir->entries[pdi];
+	if (!dir_entry->bits.present)
+		return 0;
+
+	struct page_table *table = (struct page_table *)(dir_entry->bits.address * PAGE_SIZE);
+
+	u32 pti = PTI(vaddr);
+	union page_table_entry *table_entry = &table->entries[pti];
+	if (!table_entry->bits.present)
+		return 0;
+
+	return (table_entry->bits.address * PAGE_SIZE) + (vaddr & (PAGE_SIZE - 1));
+}
+
+void virtual_map(struct page_dir *dir, struct memory_range prange, u32 vaddr, u32 flags)
+{
+	for (u32 i = 0; i < prange.size / PAGE_SIZE; i++) {
+		u32 offset = i * PAGE_SIZE;
+
+		u32 pdi = PDI(vaddr + offset);
+		union page_dir_entry *dir_entry = &dir->entries[pdi];
+		struct page_table *table =
+			(struct page_table *)(dir_entry->bits.address * PAGE_SIZE);
+
+		if (!dir_entry->bits.present) {
+			table = memory_alloc_identity(dir, MEMORY_CLEAR);
+			dir_entry->bits.present = 1;
+			dir_entry->bits.writable = 1;
+			dir_entry->bits.user = 1;
+			dir_entry->bits.address = (u32)(table) >> 12;
+		}
+
+		u32 pti = PTI(vaddr + offset);
+		union page_table_entry *table_entry = &table->entries[pti];
+		table_entry->bits.present = 1;
+		table_entry->bits.writable = 1;
+		table_entry->bits.user = flags & MEMORY_USER;
+		table_entry->bits.address = (prange.base + offset) >> 12;
+	}
+
+	paging_invalidate_tlb();
+}
+
+struct memory_range virtual_alloc(struct page_dir *dir, struct memory_range prange, u32 flags)
+{
+	u8 user = flags & MEMORY_USER;
+	u32 vaddr = 0;
+	u32 size = 0;
+
+	for (u32 i = (user ? 256 : 1) * PAGE_COUNT; i < (user ? PAGE_COUNT : 256) * PAGE_COUNT;
+	     i++) {
+		u32 addr = i * PAGE_SIZE;
+		if (!virtual_present(dir, addr)) {
+			if (size == 0)
+				vaddr = addr;
+
+			size += PAGE_SIZE;
+
+			if (size == prange.size) {
+				virtual_map(dir, prange, vaddr, flags);
+				return memory_range(vaddr, size);
+			}
+		} else {
+			size = 0;
+		}
+	}
+
+	panic("Out of virtual memory!\n");
+	return memory_range(0, 0);
+}
+
+void virtual_free(struct page_dir *dir, struct memory_range vrange)
+{
+	for (u32 i = 0; i < vrange.size / PAGE_SIZE; i++) {
+		u32 offset = i * PAGE_SIZE;
+
+		u32 pdi = PDI(vrange.base + offset);
+		union page_dir_entry *dir_entry = &dir->entries[pdi];
+		if (!dir_entry->bits.present)
+			continue;
+
+		struct page_table *table =
+			(struct page_table *)(dir_entry->bits.address * PAGE_SIZE);
+
+		u32 pti = PTI(vrange.base + offset);
+		union page_table_entry *table_entry = &table->entries[pti];
+
+		if (table_entry->bits.present)
+			table_entry->uint = 0;
+	}
+
+	paging_invalidate_tlb();
+}
+
+struct page_dir *virtual_create_dir(void)
+{
+	struct page_dir *dir = memory_alloc(&kernel_dir, sizeof(*dir), MEMORY_CLEAR);
+
+	memset(dir, 0, sizeof(*dir));
+
+	for (u32 i = 0; i < 256; i++) {
+		union page_dir_entry *dir_entry = &dir->entries[i];
+
+		dir_entry->bits.present = 1;
+		dir_entry->bits.writable = 1;
+		dir_entry->bits.user = 0;
+		dir_entry->bits.address = (u32)&kernel_tables[i] / PAGE_SIZE;
+	}
+
+	return dir;
+}
+
+void virtual_destroy_dir(struct page_dir *dir)
+{
+	assert(dir != &kernel_dir);
+
+	for (u32 i = 256; i < PAGE_COUNT; i++) {
+		union page_dir_entry *dir_entry = &dir->entries[i];
+		if (dir_entry->bits.present) {
+			struct page_table *table =
+				(struct page_table *)(dir_entry->bits.address * PAGE_SIZE);
+			for (u32 j = 0; j < PAGE_COUNT; j++) {
+				union page_table_entry *table_entry = &table->entries[j];
+				if (table_entry->bits.present) {
+					u32 paddr = table_entry->bits.address * PAGE_SIZE;
+					physical_free(memory_range(paddr, PAGE_SIZE));
+				}
+			}
+
+			memory_free(&kernel_dir, memory_range((u32)table, sizeof(*table)));
+		}
+	}
+
+	memory_free(&kernel_dir, memory_range((u32)dir, sizeof(*dir)));
+}
+
+struct page_dir *virtual_kernel_dir(void)
+{
+	return &kernel_dir;
+}
+
+/**
+ * Memory wrappers
+ */
+
+void *memory_alloc(struct page_dir *dir, u32 size, u32 flags)
+{
+	assert(PAGE_ALIGNED(size));
+
+	if (!size)
+		goto err;
+
+	struct memory_range prange = physical_alloc(size);
+	if (prange.size == 0)
+		goto err;
+
+	u32 vaddr = virtual_alloc(dir, prange, flags).base;
+	if (!vaddr) {
+		physical_free(prange);
+		goto err;
+	}
+
+	if (flags & MEMORY_CLEAR)
+		memset((void *)vaddr, 0, size);
+
+	return (void *)vaddr;
+
+err:
+	print("Memory allocation error!\n");
+	return 0;
+}
+
+void *memory_alloc_identity(struct page_dir *dir, u32 flags)
+{
+	for (u32 i = 1; i < 256 * PAGE_COUNT; i++) {
+		struct memory_range range = memory_range(i * PAGE_SIZE, PAGE_SIZE);
+
+		if (!virtual_present(dir, range.base) && !physical_is_used(range)) {
+			physical_set_used(range);
+			virtual_map(dir, range, range.base, flags);
+			if (flags & MEMORY_CLEAR)
+				memset((void *)range.base, 0, PAGE_SIZE);
+			return (void *)range.base;
+		}
+	}
+
+	return 0;
+}
+
+void memory_free(struct page_dir *dir, struct memory_range vrange)
+{
+	assert(PAGE_ALIGNED(vrange.base) && PAGE_ALIGNED(vrange.size));
+
+	for (u32 i = 0; i < vrange.size / PAGE_SIZE; i++) {
+		u32 vaddr = vrange.base + i * PAGE_SIZE;
+		if (virtual_present(dir, vaddr)) {
+			struct memory_range page_prange =
+				memory_range(virtual_to_physical(dir, vaddr), PAGE_SIZE);
+			struct memory_range page_vrange = memory_range(vaddr, PAGE_SIZE);
+			physical_free(page_prange);
+			virtual_free(dir, page_vrange);
+		}
+	}
+}
+
+void memory_map_identity(struct page_dir *dir, struct memory_range prange, u32 flags)
+{
+	assert(PAGE_ALIGNED(prange.base) && PAGE_ALIGNED(prange.size));
+
+	physical_set_used(prange);
+	virtual_map(dir, prange, prange.base, flags);
+	if (flags & MEMORY_CLEAR)
+		memset((void *)prange.base, 0, prange.size);
+}
+
+void memory_switch_dir(struct page_dir *dir)
+{
+	paging_switch_dir(virtual_to_physical(&kernel_dir, (u32)dir));
+}
+
+void memory_backup_dir(struct page_dir **backup)
+{
+	struct proc *proc = proc_current();
+	struct page_dir *dir = proc ? proc->page_dir : virtual_kernel_dir();
+	*backup = dir;
+}
+
+struct memory_range memory_range_from(u32 base, u32 size)
+{
+	u32 align = PAGE_SIZE - base % PAGE_SIZE;
+
+	if (base % PAGE_SIZE == 0) {
+		align = 0;
+	}
+
+	base += align;
+	size -= align;
+
+	size -= size % PAGE_SIZE;
+
+	return memory_range(base, size);
+}
+
+struct memory_range memory_range_around(u32 base, u32 size)
+{
+	u32 align = base % PAGE_SIZE;
+
+	base -= align;
+	size += align;
+
+	size += PAGE_SIZE - size % PAGE_SIZE;
+
+	return memory_range(base, size);
+}
+
+extern u32 kernel_start;
+extern u32 kernel_end;
+static struct memory_range kernel_memory_range(void)
+{
+	return memory_range_around((u32)&kernel_start, (u32)&kernel_end - (u32)&kernel_start);
+}
+
+void memory_install(struct mem_info *mem_info, struct vid_info *vid_info)
+{
+	for (struct mmap_boot *p = mem_info->start; (u32)(p - mem_info->start) < mem_info->size;
+	     p++) {
+		if (p->hbase || !p->acpi || !p->type)
+			continue;
+
+		u32 size = p->lsize;
+		if (p->hsize)
+			size = U32_MAX - p->lbase;
+
+		/* printf("Memory region: %x-%x\n", p->lbase, p->lbase + size); */
+		if (p->type == MEMORY_AVAILABLE) {
+			physical_set_free(memory_range_around(p->lbase, size / PAGE_SIZE));
+			memory_total += size;
+		} else if (p->type == MEMORY_DEFECT) {
+			printf("Defect memory at 0x%x-0x%x!\n", p->lbase, p->lbase + size);
+		}
+	}
+
+	for (u32 i = 0; i < 256; i++) {
+		union page_dir_entry *dir_entry = &kernel_dir.entries[i];
+		dir_entry->bits.present = 1;
+		dir_entry->bits.writable = 1;
+		dir_entry->bits.user = 0;
+		dir_entry->bits.address = (u32)&kernel_tables[i] / PAGE_SIZE;
+	}
+
+	memory_used = 0;
+	printf("Detected memory: %dKiB (%dMiB)\n", memory_total >> 10, memory_total >> 20);
+
+	// Map kernel
+	memory_map_identity(&kernel_dir, kernel_memory_range(), MEMORY_NONE);
+
+	// Map kernel stack
+	memory_map_identity(&kernel_dir, memory_range_around(STACK_START - STACK_SIZE, STACK_SIZE),
+			    MEMORY_NONE);
+
+	// Map VBE data
+	memory_map_identity(&kernel_dir, memory_range_around((u32)vid_info->vbe, 0x1000),
+			    MEMORY_NONE);
+
+	// Unmap NULL byte/page
+	struct memory_range zero = memory_range(0, PAGE_SIZE);
+	virtual_free(&kernel_dir, zero);
+	physical_set_used(zero);
+
+	memory_switch_dir(&kernel_dir);
+	paging_enable();
+}